Displaying a Character Counter for Multiline Textboxes

Many Textbox fields restrict the number of characters entered in them for the sake of business validation. With single line textboxes it is just a matter of setting the MaxLength property. However, MaxLength property doesn't work as expected for multiline textboxes. When you set the TextMode property of ASP.NET TextBox control to MultiLine the Textbox control is rendered as a TEXTAREA element which doesn't support this property. Developers often use custom client side JavaScript code to enforce that only a certain number of characters are entered into a multiline textbox. Wouldn't it be easy if you can enforce this restriction without touching the Textbox control markup or its server side code? ...